Mechanochemical Reactions of PVC-CaO/Ca(OH)2 and PVDF-NaOH Systems by Ball Milling

Publication Reference: 
Author Last Name: 
Fumio Saito, Qiwu Zhang and Junya Kano
Report Type: 
Research Area: 
Size Reduction
Publication Year: 
Publication Month: 

PVC ([CHZCHCI] n) powder with fine CaO and/or Ca(OIQ powder and PVDF ([CH$ZF&,) powder with NaOH powder were ground in air by a planetary ball mill to investigate their mechanochemical reactions. The ground mixture was washed with distilled water to remove soluble compounds in the ground product by filtration. Reaction yield was determined by measuring the concentration of halogen in the filtrate. In addition, for the system of PVDF-NaOH, the filtrate containing soluble organic compounds was regulated with HCl solution to decrease its pH to 2, then ethyl acetate was put in the filtrate to extract the organic compounds.

All the same, the grinding causes dehalogenating reaction, forming CaOHCl and polyetylene ([CH=CI&) from the former system, and NaF and organic phases such as [CH2-C=O], and [GC] from the latter one.

For the PVC and CaO/Ca(OH)Z system, the grinding enables to accelerate the dehydrochlorinating reactions between. However, the reactivity of CaO is superior to that of Ca(OHJ2, due to the formation of Hz0 in the PVC-Ca(OH)z system. PVC is transformed into partly dehydrochlorinated polymer, while CaO/Ca(OH)2 is changed into chloride form. The mechanochemically formed CaOHCl in the ground mixture can be removed out by washing with water. The dechlorination is improved with an increase in the molar ratio of (CaO/PVC) as well as grinding time. The impact energy of balls simulated by the PEM would be one of the important parameters governing the mechanochemical reaction between PVC and CaO/Ca(OH)2.

Mechanochemical reaction between PVDF and NaOH proceeds rapidly to transfer nearly half of total fluorine into NaF through the displacement of fluorine in PVDF by OH base. When both fluorine bases bound to the same carbon atom are replaced by OH-base, the dehydration takes place to generate water, which plays a significant role to cause the strong agglomeration of fine particles during grinding. About 90% of fluorine in PVDF can be transferred into NaF by grinding. Dehydration of polar CH2C(OH)2 base proceeds in two ways to form carbonyl (C=O) base and carbon double binding. This gives us water soluble and insoluble organic compounds formed in the ground product.